U.S. Pat. Nos. 4,823,408 and 4,905,324, disclose a useful electrically actuated incinerator toilet and useful ash pans for use with the incinerator toilet.
Higher efficiency in the use of electrical energy produced by the electric heater of an electrically actuated incinerator toilet is needed in order to reduce the time of incineration or to increase the rate of incineration and hence the capacity of the toilet for reducing the cost of operation, i.e. kilowatt consumption.
Greater efficiency can be obtained by reducing the volume of the incinerator chamber, particularly the space immediately surrounding the heater. If all heaters were of the same wattage and hence the same coil diameter, then the inner wall of the chamber directly facing the heater could be assigned a fixed, best size diameter. Since however, heaters do vary in wattage, depending upon the application, as do the diameters of the heaters, a means is needed to accommodate the varying diameters accompanied by the minimization of space immediately behind the heater coil.
Better efficiency also can be achieved by improving the efficiency of the ash pan.
An ash pan formed by an aluminium insert placed into a stainless steel pan has advantages but it also has been found to have several shortcomings.
Aluminum has a melting point around 1170 deg F. but begins to soften at considerably lower temperatures with the result that the sides of the insert under certain conditions can sag and rupture at operating temperatures of the incinerator; in particular, hot spots can develop immediately beneath waste matter which is burning (exothermic). There tends to be corrosion also at the higher temperatures. The overall result is that the aluminum inserts have to be replaced too often.
Aluminum has a relatively high coefficient for heat conduction, i.e. around 0.5 units as compared to stainless steel having a coefficient for heat conduction of about 0.1 units. Copper has the highest coefficient of heat conduction of commonly available material: 1.0 units. Clearly, if the objective is to provide means to pick up heat from side portions of the insert and conduct it to the bottom section underneath the waste, then copper would be much better than aluminum (1.0 to 0.5); however, copper oxidizes rapidly at the temperatures expected during the incineration process. Furthermore, copper is soft and cannot take the physical abuse associated with cleaning and handling of the ash pan during routine maintenance of the toilet.